Access to Polysulfides through Photocatalyzed Dithiosulfonylation.

In this study, we outline a general method for photocatalyzed difunctionalization of alkenes, a diene, alkynes, 1,3-enynes, and [1.1.1]propellane using dithiosulfonate reagents (ArSO2 -SSR) with improved atom economy. Both "ArSO2 -" and "-SSR" on the dithiosulfonate are transferred under mild conditions with broad substrate scope, high stereoselectivity, and complete regioselectivity. Significantly, the resulting dithiosulfonylated styrene is a general and practical nucleophilic disulfuration reagent, reacting with a variety of electrophiles efficiently. Both reactions can be conducted on gram scale, rendering the approach highly valuable.

Convergent Synthesis of 1,4-Dicarbonyl Z-Alkenes through Three-Component Coupling of Alkynes, α-Diazo Sulfonium Triflate, and Water.

We report a general protocol for the convergent synthesis of 1,4-dicarbonyl Z-alkenes form alkynes using α-diazo sulfonium triflate and water. The C═O, C═C, and C-H bonds are formed under mild conditions with a wide range of functional groups tolerated. The reaction exhibits excellent Z-selectivity and complete regioselectivity. The resulting 1,4-dicarbonyl Z-alkenes can smoothly undergo follow-up conversion to a variety of heteroaromatic scaffolds. Moreover, the reaction also provides a facile access to the corresponding deuterated Z-alkenes and deuterated heteroarenes with a high level of deuterium incorporation (90-97% D-inc.) by directly using D2O, thus rendering the method highly valuable. The comprehensive mechanistic studies indicate that a free carbyne radical intermediate is formed via the photocatalytic single electron transfer process, and KH2PO4 plays a crucial role in significant improvements on yield and selectivity based on density-functional theory calculations, providing a new direction for radical coupling reactions of diazo compounds.

Chemoselective Mono- and Difluorination of 1,3-Dicarbonyl Compounds.

By altering the amount of Selectfluor, the highly selective mono- and difluorination of 1,3-dicarbonyl compounds has been achieved, affording a variety of 2-fluoro- and 2,2-difluoro-1,3-dicarbonyl compounds in good to excellent yields. The reaction can be readily performed in aqueous media without any catalyst and base, which features practical and convenient fluorination. Importantly, a gram-scale reaction, transformation of 2-fluoro-1,3-diphenylpropane-1,3-dione to 4-fluoro-1,3,5-triphenyl-1H-pyrazole, and chlorination and bromination of 1,3-dicarbonyl compounds are realized to further exhibit its synthetic utility.

Dual Roles of tert-Butyl Nitrite in the Transition Metal- and External Oxidant-Free Trifluoromethyloximation of Alkenes.

By employing tert-butyl nitrite as both nitrogen source and oxidant, the trifluoromethyloximation of alkenes proceeds smoothly in a free-radical process. The developed difunctionalization reaction enables practical and efficient synthesis of a wide range of α-CF3 ketoximes in moderate yields with excellent regioselectivity. This method features the use of readily available and stable alkenes as substrates and inexpensive CF3 SO2 Na as a CF3 reagent, no involvement of transition metals or external oxidant, and room-temperature conditions. Moreover, a scale-up of the reaction, further transformation of the products into various valuable CF3 -containing compounds, and removal of the trifluoromethyl group are readily achieved.

K2S2O8-Mediated Selective Trifluoromethylacylation and Trifluoromethylarylation of Alkenes under Transition-Metal-Free Conditions: Synthetic Scope and Mechanistic Studies.

A practical and efficient method for selective intramolecular radical trifluoromethylacylation and -arylation of alkenes with inexpensive CF3SO2Na and K2S2O8 in aqueous media has been developed, respectively, affording the highly chemoselective synthesis of CF3-functionalized chroman-4-ones and chromanes in satisfactory yields. Control experiments and DFT calculations indicate that the CF3SO2Na/K2S2O8 system is capable of trifluoromethylating the substrate of alkenes without a transition metal catalyst and the oxidation of CF3SO2Na to ·CF3 by K2S2O8 is involved in the rate-determining step.